Since the time it was discovered that the pumping heart was central to maintaining life, medical science has developed new and improved ways to monitor cardiac function and to diagnose cardiac dysfunction. Currently, the electrocardiograph or "EKG" (alternatively, "ECG")is considered the best method for monitoring cardiac function.
The electrocardiograph instrument monitors cardiac function by recording changes in electrical potential detected by electrodes attached at various locations on the monitored patient's skin. The electrodes measure fluctuations in electric potential caused by depolarization and repolarization of the cardiac muscle during each heartbeat. The EKG instrument translates the fluctuations in electric potential at various locations into a set of traces on an electronic screen or paper "rhythm strip" chart, producing the familiar spiked beat pattern. The magnitude and timing of various fluctuations as represented by a trace or rhythm strip are then analyzed to provide information relating to heart rate, coordination between the various chambers of the heart, condition of the heart tissue and cardiac dysfunction.
An individual trace or rhythm strip is a representation of data collected from one electrode "lead". A "lead" is a combination of two electrodes which produces an electropotential "picture" of the heart from a given angle. Though electrodes can be placed at many different locations on a patient's skin, the placement of electrodes at ten specific locations on the patient's skin have been set by convention. The ten standard electrode locations produce a total of twelve different "conventional leads."
Many EKG instruments monitor all twelve conventional leads, providing very detailed and comprehensive data concerning cardiac function. Some instruments can selectively monitor and record a collection of three, four or six leads selected by the user. Other instruments monitor all twelve leads simultaneously and display three, four, six or twelve traces at a time and incorporate the ability to display different lead configurations during an EKG examination. All of these systems produce traces on a monitor or a rhythm strip as the data is collected.
Unfortunately, obtaining a complete conventional twelve-lead diagnosis requires (1) an instrument which is usually both expensive and, as a result of its size, difficult to transport easily; (2) the presence of a physician or EKG technician at the site where the data is collected; and (3) an examination which is invasive for the patient since the patient must be disrobed above the waist and, in some cases, shaved so that certain of the electrodes can be attached to the chest. While monitoring a subset of the twelve lead system alone may provide sufficient data to recognize many features of cardiac function and dysfunction, one-lead and two-lead systems may not allow a physician or EKG technician to differentiate particular arrythmic conduction disturbances or ischemic events.
In many situations, including home-based post-operative care, patient screening and outpatient surgical procedures, it is desirable to monitor cardiac activity and to detect irregularities therein without making the complete diagnosis provided by a conventional twelve lead EKG instrument. For example, during many dental and oral surgery procedures the patient is exposed to extreme physiological stress which can result in cardiac dysfunction or arrest. By monitoring the patient's cardiac function before treatment, during treatment and/or when signs of extreme stress (heavy breathing, accelerated pulse) are observed the quality of patient care is increased and a cardiac event may be averted.
Although non-cardiology professionals, including dentists and outpatient surgeons, are interested in monitoring the heart function of their patients before, during and after stressful procedures, they seldom use EKG technology because of the sizeable cost of EKG instruments and because of their lack of expertise in reading EKG data. Consultation with a cardiologist or EKG technician is usually necessary to translate the EKG data into information useful to the treating professional. Few non-cardiology professionals have such resources readily available and, as a result, the effects of stressful procedures upon patient cardiac function are often not monitored. Even when non-cardiology professionals have sought the counsel of cardiologists, e.g., in extreme emergency situations during a procedure, the cardiologist is greatly hindered by the inability to examine any EKG data. Unless the cardiologist is present with the patient, it is often impossible to make a useful determination of the patient's condition without an EKG trace.
It would, therefore, be desirable to provide a simple, economical and non-invasive method and system to collect a clinically significant sample of electrocardiographic data. Preferably, such data should be collected in a manner such that it can be easily communicated to a cardiologist or EKG technician for interpretation.